Alien life is probably purple and not green: research

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The possibility of purple aliens

What’s the story

The search for extraterrestrial life has taken an intriguing turn, with scientists now proposing that alien life may be purple instead of green.

This hypothesis challenges our Earth-centered perspective of life, which is predominantly green due to the oxygen-producing photosynthesis performed by organisms containing the green pigment chlorophyll.

A research team from Cornell University suggests that life on an Earth-like planet orbiting another star could appear very different and could possibly be dominated by purple bacteria.

Purple bacteria: the potentially dominant life on alien worlds

Purple bacteria use invisible infrared radiation for photosynthesis in environments with little/no visible light or oxygen.

These organisms contain purple pigments and can produce a unique ‘light fingerprint’ that can be detected by advanced telescopes on the ground and in space.

Coelho, a postdoctoral fellow at the Carl Sagan Institute (CSI) and lead author of the study, stated that “purple bacteria can thrive under a wide range of conditions, making it one of the main contenders for life that could inhabit a variety of worlds.” can dominate. .”

The importance of a life signs database

The researchers emphasize the need to establish a database for signs of life to ensure that potential alien life forms are not overlooked.

Kaltenegger, CSI director and associate professor of astronomy, emphasized, “We need to create a database for signs of life to ensure that our telescopes don’t miss life when it happens.”

The CSI team is currently working to catalog the colors and chemical signatures that different organisms and minerals would exhibit in the reflected light from an exoplanet.

Purple bacteria: thrive on energy-efficient light

The CSI team collected samples of more than twenty species of purple sulfur and purple non-sulfur bacteria from different environments.

These bacteria thrive on low-energy red or infrared light using simpler photosynthetic systems that absorb infrared and do not produce oxygen.

Coelho noted that these organisms, thought to have been common on early Earth before the rise of plant-type photosynthesis, could be particularly suited to planets orbiting cooler red dwarf stars, the most common star type in our Milky Way.

The potential dominance of purple bacteria on alien worlds

After studying the biopigments and light fingerprints of the purple bacteria, the researchers simulated Earth-like planets with varying conditions and cloud cover.

They found that both wet and dry purple bacteria produced intensely colored biosignatures in a range of simulated environments.

Coelho stated, “If purple bacteria are thriving on the surface of a frozen Earth, an ocean world, a snowball Earth, or a modern Earth orbiting a cooler star, we now have the tools to look for it.”